The present invention relates to a sheet-like material which is formed to have three dimensional surface features with spaces therein to contain a substance, and more particularly to such materials wherein the surface features prevent external surfaces from contacting the substance until forces exerted on the surface features cause them to deform. The present invention further relates to methods of making such sheet-like materials.
There exist articles which are coated or impregnated with useful substances intended to be utilized when the article is contacted with a target surface. While there are advantages with having the substance present on or near the surface of such articles, there is often the drawback that the useful substance is unprotected and is subject to inadvertent contact before intended use. One broad category of such articles encompasses the area of tapes and labels.
In the art of tapes, labels, and other articles using pressure sensitive adhesive to adhere an adhesive coated surface to a target surface, there has been recognized the problem of premature sticking to the target surface. That is, before the adhesive coated surface can be properly positioned over a target surface, inadvertent contact of the adhesive with the target surface causes premature sticking at one or more locations, thereby inhibiting proper positioning. Premature sticking may also cause contamination or degradation of the adhesive prior to final positioning at the target surface.
Others have attempted to overcome this problem by providing standoffs on a material surface, between which adhesive elements are located. Standoffs include any means extending outwardly from an adhesive surface which is contacted first before the adhesive surface is exposed to contact by another surface. Protecting an adhesive from premature contact by another surface has been achieved by adding strips of polymer foam to form deformable standoffs on an adhesive surface, for example. Polymer foams, however, tend to spring back and exert a peel force on the adhesive bond to the target surface. Thus, a more aggressive adhesive may be required to overcome this undesirable peel force.
U.S. Pat. No. 5,141,790 to Calhoun et al. discloses one-time repositionable pressure sensitive tapes with an adhesive coated surface having clumps of particles spaced out on the adhesive to keep the adhesive from touching a target surface until the sheet is pressed against the target surface. The particles are smaller than the thickness of the adhesive layer so that when pressed, the particles sink below the surface of the adhesive and no longer provide their spacing function. Since adhesive may be the most expensive component of a tape, and since the overall surface is coated with a thick layer of adhesive, Calhoun et al. would offer an expensive solution.
U.S. Pat. No. 4,061,820 to Magid et al. discloses a foam with cells. The foam is compressed to open cell cavities at the foam surface so that pressure sensitive adhesive can be applied to the open cells. When the foam is released, the cells close and hide the adhesive. When the foam is pressed, the cells bring pressure sensitive adhesive to the surface for sticking the foam to a target surface. This too is believed to be an expensive solution to the problem, and defining continuous or interconnected patterns of adhesive would not be possible. Also, polymer foams provide undesirable spring back force, which acts to undo the adhesive bond to a target surface. Furthermore, in some applications transparency may be beneficial, such as for accurate placement, and the foam of Magid et al. would not be transparent.
U.S. Pat. No. 4,959,265 to Wood et al. discloses an adhesively coated substrate having bluntly pointed stems protruding beyond a layer of pressure sensitive adhesive. The back of this substrate may be bonded to a sanitary napkin. The napkin may then be installed onto a foraminous fabric by pressing to force the stems to penetrate the fabric to a depth where the fabric contacts the adhesive. By penetrating fabric, the stems significantly reinforce the adhesion of the fastener. The stems should be resistant to compression and bending, even thought they may be quite supple. The backing with its stems preferably is formed from a tough thermoplastic resin by cast molding or extrusion molding. The stems protrude 20 microns to 3 mm above the adhesive level, depending on the coarseness of the fabric to be penetrated. The adhesive area is preferably between 3 and 30 times the area occupied by the stems. Rigid target surfaces are obviously inoperable with Wood et al.
U.S. Pat. No. 5,344,693 to Sanders discloses a substrate having a plurality of non-interconnecting spacing means extending outwardly from an adhesive coated surface to space the surface from another surface until the surfaces are pressed together. The spacing means of Sanders is non-deformable. The spacing members are spaced up to 80 times the dimension of each spacer. Since few spacing members provide the standoff function, Sanders would need a stiff web between members as well as stiff members to prevent inadvertent adhesive contact. Stiffness in Sanders"" configuration corresponds to thick, and therefore expensive materials. Sanders discusses his invention for use with reclosable bags. Sanders, like Wood et al., would not be compatible with rigid target surfaces where the members deform instead of the target surface.
A commonly assigned, co-pending U.S. patent application, Ser. No. 08/584,638, filed Jan. 10, 1996 by the same inventors as in the present application, discloses a film formed to have deformable hollow protrusions which are very closely spaced and a continuous layer of pressure sensitive adhesive located between the protrusions. This co-pending application is hereby incorporated herein by reference. The close spacing between protrusions enables the web material to be very thin and flexible yet resistant to inadvertent deformation because of the high density of standoffs per unit area However, the co-pending application focuses on formed films which have pressure sensitive adhesive between protrusions. The same inventors have discovered much broader constructions for their new material, as well as alternative methods of making it.
Methods for making articles and surfaces having adhesive surfaces protected by standoffs are disclosed, for example, in U.S. Pat. No. 5,453,296 to Lauritzen et al. Lauritzen et al. describes methods for making a sanitary napkin which has a recessed adhesive pattern for attaching it to a user""s undergarment. Lauritzen et al. forms depressions in a fluid-impervious barrier film. The depressions create raised areas in the barrier film on the side of the napkin which attaches to the undergarment. Adhesive is placed onto the barrier film side having the raised areas in discrete patterns between the raised areas. In an alternative, Lauritzen et al. applies adhesive to the tips of the raised areas of the barrier film and then inverts the raised areas to form depressions. The adhesive is thereby conveniently placed in the depressions. Lauritzen et al.""s discrete adhesive placement fails to enable an air-tight adhesive seal with a target surface, however.
Lauritzen et al. also notes that standoffs must be formed such that they are strong enough to protect the adhesive from inadvertent contact during shipping and storage, yet are deformable for activation. Lauritzen et al. states that sufficient rigidity is available from 0.03 inch (0.08 cm) to 0.06 inch (0.15 cm) thick foam. In one embodiment, conical depressions have diameters at their open ends of 0.1 inches (0.25 cm) to 0.5 inches (1.27 cm) and depths of 0.1 inches (0.25 cm) to 0.25 inches (0.64 cm). Such large depressions and thick foam preclude the ability to wind up the material in a compact roll for consumer delivery. Also, large sized standoffs provide greater opportunity for an interrupted seal instead of a continuous seal, especially when dealing with a narrow target surface. Smaller, more closely spaced standoffs increase the frequency of adhesive contact to the target surface to better approximates a continuous seal.
In still another Lauritzen et al. embodiment, a printing device transfers adhesive to a printing belt, which transfers adhesive to a release belt, and then to the barrier foam web. This system is used to first print a pattern of discrete patches of adhesive onto the barrier foam web. Then the foam web is registered with a vacuum plate. When each patch of adhesive is disposed above a recess in the forming plate, vacuum forms adhesive containing depressions. Because of registration requirements, the invention is believed limited to relatively large and well spaced standoffs. A fine pattern of very small standoffs would be difficult to make using Lauritzen et al.""s methods because registration for forming would require high accuracy. Lauritzen et al.""s methods are believed to limit material constructions to those having macro patterns of low number density of standoffs, compared to the micro pattern of high number density of standoffs of co-pending U.S. patent application, Ser. No. 08/584,638.
It is an object of the present invention to provide a three dimensional structure for containing a layer of substance therein, the substance staying therein until the three dimensional structure is deformed into a substantially two dimensional structure or otherwise activated to expose or release the substance,
It is another object of the present invention to provide a deformable, sheet-like material having a three dimensional surface comprising deformable protrusions, between which a substance is placed internal to the outermost ends of the protrusions in a continuous or interconnected pattern, wherein the substance is contactable by an external surface only after the protrusions are deformed to the level of the substance.
It is still another object of the present invention to provide a deformable material having deformable protrusions which is sufficiently thin to be wound onto compact rolls for storage and convenient packaging, yet having sufficient resistance to the deformation of protrusions in order to prevent premature deformation due to in-wound web tension, etc., while the material is stored in roll form.
It is yet another object of the present invention to provide a deformable material having deformable protrusions containing adhesive within or therebetween, which once deformed, stay deformed with minimal spring back so that adhesive exposed to contact with a target surface need not be overly aggressive in order to remain bonded to the target surface.
It is still another object of the present invention to provide a material including a very thin, finely patterned, three dimensional structure having a recessed substance layer, such that the material is substantially transparent or translucent so that it may be accurately positioned before deforming the structure to expose the substance layer.
It is a further object of the present invention to provide methods for making a very thin, finely patterned, three dimensional structure having a recessed substance layer accurately registered with deformable protrusions, wherein the method is capable of automated continuous motion or indexing motion for a continuous web format.
In the present invention, the term xe2x80x9csubstancexe2x80x9d can mean a flowable substance which is substantially non-flowing prior to delivery to a target surface. xe2x80x9cSubstancexe2x80x9d can also mean a material which doesn""t flow at all, such as a fibrous or other interlocking material. xe2x80x9cSubstancexe2x80x9d may mean a fluid or a solid. xe2x80x9cSubstancexe2x80x9d is defined in this invention as any material capable of being held in open valleys and/or depressions of a three dimensional structure. Adhesives, electrostatics, mechanical interlocking, capillary attraction, surface adsorption, and friction, for example, may be used to hold the substances in the valleys and/or depressions. The substances may be permanently held in the valleys and/or depressions, or the substances may be intended to be released therefrom when exposed to contact with external surfaces or when the three dimensional structure is deformed, heated, or otherwise activated. Of current interest in the present invention include substances such as gels, pastes, foams, powders, agglomerated particles, prills, microencapsulated liquids, waxes, suspensions, liquids, and combinations thereof.
The spaces in the three dimensional structure of the present invention are normally open; therefore it is desirable to have substances stay in place and not run out of the structure without an activation step. The activation step of the present invention is preferably deformation of the three dimensional structure by compression. However, an activation step to cause substance to flow could be heating the material to above room temperature or cooling it below room temperature. Or it could include providing forces excessive of the earth""s gravity. It could also include other deforming forces, such as tensile forces and combinations of these activation phenomena.
The term xe2x80x9cdeformable materialxe2x80x9d is intended to include foils, polymer sheets, cloth, wovens or nonwovens, paper, cellulose fiber sheets, co-extrusions, laminates, and combinations thereof. The properties of a selected deformable material can include, though are not restricted to, combinations or degrees of being: porous, non-porous, microporous, gas or liquid permeable, non-permeable, hydrophilic, hydrophobic, hydroscopic, oleophilic, oleophobic, high critical surface tension, low critical surface tension, surface pre-textured, elastically yieldable, plastically yieldable, electrically conductive, and electrically non-conductive.
In one aspect of the present invention, a substance delivery system comprises a three dimensional structure having outermost surface features and interconnected spaces for containing a substance. The substance has a level internal to the outermost surface features such that the substance is protected from inadvertent contact with external surfaces. A substance having substantial resistance to flow prior to delivery to a target surface occupies the interconnected spaces of the three dimensional structure. The substance remains protected until the three dimensional structure is sufficiently deformed into a substantially two dimensional structure and the substance is thereby exposed to contact an external surface without compliance of the external surface being necessary. The number density of the outermost surface features is greater than 200 outermost surface features/square inch or 31 surface features/square cm.
The three dimensional structure may be deformed by a compression force applied substantially perpendicular to a plane of the three dimensional structure, thereby causing the outermost surface features of said three dimensional structure to deform in a direction of the compression force. Alternatively, the three dimensional structure may be deformed by a tensile force applied substantially parallel to a plane of the three dimensional structure, thereby causing the outermost surface features of the three dimensional structure to deform in a direction substantially perpendicular to the plane. Also, the three dimensional structure may be deformed by a combination of a tensile force applied substantially parallel to a plane of the three dimensional structure and a compression force applied substantially perpendicular to the plane, thereby causing the outermost surface features of the three dimensional structure to deform substantially perpendicular to the plane.
In another aspect of the present invention, a method of making a three dimensional material having outermost surface features and having spaces for containing a substance internal to the outermost surface features, such that the substance is protected from inadvertent contact with external surfaces, comprises the steps of coating a substance onto a forming surface, transferring the coating of substance from the forming surface to a piece of material, and forming the piece of material into a three dimensional structure on the forming surface while the substance is still in contact with the forming surface. This method accurately registers the three dimensional structure with the substance so that the substance may be located within the spaces of the three dimensional structure internal to the outer most features thereof. A further step of this method may include providing the forming surface with a low critical surface tension so that the substance will adhere more readily to the piece of material than to the forming surface.
In yet another aspect of the present invention, a method of making a material, which has a substance protected from inadvertent contact with an external surface until the material is deformed, has a first step of coating a forming screen with a first substance. The forming screen has a top surface and a plurality of recesses therein. The coating step applies the first substance to the top surface without bridging the recesses. A second step includes introducing a piece of material, which has a first side and a second side, onto the forming screen such that the first side is in contact with the first substance on the top surface of the forming screen. The first substance preferentially adheres to the first side of the piece of material. A third step includes forming the piece of material to create a plurality of hollow protrusions extending from the first side into the recesses of the forming screen. The plurality of hollow protrusions are spaced apart by valleys into which the first substance is transferred from the forming screen. The plurality of hollow protrusions are accurately registered with the first substance by use of a common transfer and forming surface. The first substance forms an interconnected layer in the valleys between the protrusions.
The piece of material has a plurality of depressions on the second side corresponding to the plurality of hollow protrusions. The method may further comprise the step of injecting a second substance into the plurality of depressions on the second side of the piece of material. Alternatively, the method may further comprise the step of forming an aperture at the outermost end of each of the plurality of protrusions. The step of introducing the material onto the forming screen may include metering a web onto the forming screen or extruding the material directly onto the forming screen. The method may further comprise the step of removing the piece of material from the forming screen, preferably without leaving a residue of substance on the forming screen.
In still another aspect of the present invention, a method of making a material, which has a substance protected from inadvertent contact with an external surface until the material is deformed, has the first step of coating top surfaces of pins extending from a forming plate with a first substance. The pins are separated from each other by spaces. The coating step applies the first substance to the top surfaces of the pins without bridging across the spaces. A second step introduces a piece of material having a first side and a second side onto the pins such that the first side is in contact with the first substance on the top surface of the pins. The first substance preferentially adheres to the piece of material. A third step includes forming over the pins of the forming plate the piece of material to create a plurality of hollow protrusions extending from the second side. The plurality of hollow protrusions have depressions registered with the pins which have discrete spots of the first substance therein. The piece of material has an interconnected valley formed on the second side corresponding to the spaces between the pins.
The step of introducing the material onto the pins may include metering a web onto the pins or extruding the material directly onto the pins. As an alternative, the method may further comprise the step of forming an aperture in the interconnected valley between each of the plurality of protrusions. The method further comprises the step of removing the piece of material from the pins, preferably without leaving a residue of substance on the pins.
In a further aspect of the present invention, a piece of material has a substance therein protected from inadvertent contact with an external surface until the material is deformed. The piece of material comprises a piece of deformable material which has a first side formed to have a plurality of hollow protrusions separated by valleys. The plurality of hollow protrusions have outermost ends. The piece of material has a second side. The second side has a plurality of depressions therein corresponding to the plurality of hollow protrusions on the first side. The substance adheres to and partially fills the valleys between the plurality of hollow protrusions. The substance has a surface below the outermost ends of the plurality of hollow protrusions, so that when a portion of the first side of the piece of deformable film is placed against a target surface, the plurality of hollow protrusions prevent contact between the substance and the target surface until the portion is deformed at the target surface. Preferably, the plurality of protrusions deform by modes which are selected from the group consisting of inverting, crushing, and elongating. Preferably, in the inverting and/or crushing modes, each of the plurality of protrusions will not substantially deform until exposed to a pressure of at least 0.1 pounds per square inch (0.69 kPa).
The valleys contain a substance in at least a portion thereof. Preferably, the valleys have an interconnected layer of substance therein such that contact of the substance with the target surface forms a continuous pattern. The substance adheres preferentially to the first side of the piece of material. The plurality of depressions on the second side may also have a substance injected therein, which may be the same as or different than the substance transferred to the first side.